1. Field
One or more embodiments of the present invention relate to a method and system for detecting a shadow and a highlight, and a recording medium thereof, and more particularly, to a method and system capable of detecting a shadow and a highlight in a surveillance camera, and recording medium thereof.
2. Description of the Related Art
Surveillance cameras are widely used in public places for security purposes. However, additional labor is required to inspect and determine whether a critical incident occurred or is occurring. Therefore, a surveillance system with an intelligent camera that can detect, track, and analyze actions of a human being and other objects is a focus of much research.
Detecting and tracking of a moving object is at the core of many applications that process image sequences. The applications generally attempt to identify an appearance of the moving object and a shadow that moves along with the moving object in a scene. When a foreground is misclassified as a shadow point and thereby the moving object is separated and extracted, the shadow may cause a serious problem. Specifically, due to the shadow cast over another object, the merging of objects, shape distortion of the objects, and loss of the objects may occur.
Since a shadow and a related object generally share two important visual features outlined below, detection of the shadow may be difficult. First, the shadow point is significantly different from a background and thus is detectable as the foreground. Second, the shadow has the same motion as its corresponding object. For this reason, identifying the shadow is critical for still images and image sequences, for example, a video. Currently, the identification of shadows has become an active research area.
Generally, there are three types of schemes for identifying a shadow region and an object region.
A first scheme is based on the assumption that a system is aware of each of a light source, an object shape, and a ground plane. Therefore, when there is a combined region of shadow and object, the first scheme may predict which region is the object and which region is the shadow cast by the object.
A second scheme is based on image constancy. Color constancy indicates that a luminance is reduced in a shadow region to thereby decrease the intensity of a corresponding pixel. However, there is a relatively small change in the hue and saturation of the pixel. Therefore, the second scheme tests hue and saturation information to identify the shadow and the object. Also, texture constancy indicates that even though the intensity is reduced in the shadow region, an edge of the shadow region does not move. However, in the case of a foreground object, both edge and intensity are changed.
A third scheme is based on the edge width. The shadow region includes a complete shadow region and a partial shadow region. The partial shadow region corresponds to a narrow ribbon between the complete shadow region and the background. Also, the partial shadow region corresponds to a portion that gradually changes from the background to the complete shadow region. Therefore, the edge of the shadow region is wide and smooth, whereas the edge of the object region is narrow and sharp.